Heat-treating apparatus



Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE LAIENOE BOSS GALE STEWABT .AND CLABENCE JOHN ZERN, OF LA GRANGE, ILLINOIS, ASSIGNORS TO WESTEBN ELECTRIC COMPANY, INCORPOMTED, OF NEW YORK, N. Y.,

.A. COBPOBATION OF NEW 'YORK HEAT-TREATING AP PARATUS Application mea November 15, me, Serial No. 148371. Rencwed September 23. 1930.

This invention relates to heat treating apparatus, and more particularly to electromagnetic heat treating furnaces.

In the process of hardening certain metallic parts', it is common practice in some instances to subject the parts to heat `within a furnace and then quench the heated parts in a bath of oil, water or other suitable quenching material. Thus, for example, in order to eflect the proper hardening of parts, such as magnets, they should be heated to the proper or critical temperature preliminary to the quenching operation. This critical temperature is sometimes designated as the non-magnetic point for the reason that when certain magnetic materials 'are heated 'to a temperature which lies within the socalled critical range 'they immediately lose all of their magnetc properties.

The primary object of this invention is to provide simple and efiective apparatus to facilitate the heatingof work to a proper temperature.

In accordance with the general features of the invention, one embodiment thereof comprises an electrical heat treating furnace provided with a lead bath and a strong electro-magnet arranged to attract and thereby retain steel parts or the like within the molten lead in the bottom of the lead container. The

electro-magnet retains the parts in the bottom of the container until they are heated to their critical temperature, at which point they lose their magnetic properties and rise to the surface of the lead bath.

These and other objects will be apparent from the following detailed descripton and the accompanying drawing wherein a heat treating furnace representing one embodiment of the invention is disclosed.

Referring now to the drawing, it will be observed that an upright cylindrical furnace housing 10 constructed of any suitable refractory material is surrounded by a shell or metallic casing 11. A depression is provided within the upper portion of the furnace housing 10 to accommodate a crucible 13 constructed of any suitable heat resisting material, such as graphite. Encircling 50 the crucible 13 is a heating coil or element 14 which is supported in position by means of nsulating mountings 16.' The heating coil 14 forms a part of an electrical circuit which includes a suitable source of alternating current supply 17 and a switch 18. The coil 14 upon the closing of the switch 18 serves to heat a bath 19 of treating material, such as lead or other material having a relatively hi h specific gravity.

ositioned beneath the cruciblev13 within a recess 20 provided in the lower portion of the furnace housing 10 is an electro-magnet 21. This magnet, which com rises a soft ron core 23 within a coil wnding 24, is separated from the bottom of the crucible 13 by a block of suitable heat insulating material 26, the coil 24 being electrically con nected with a battery 27 included within a crcuit provided with a switch 28.

In the operation of the furnace the switch 18 is closed and the current flow through the heating coil 14 may be controlled by means of an ad'ustable resistance 30 so as to heat the lead ath 19 to the desired temperature. Work, such as the U-shaped magnets shown by dot and dash lines, may be dropped into the molten lead, and upon the closing of the switch 28 the electro-magnet 21 will be energized sufiiciently to attract the work toward the bottom of the bath. The work will be retained in the designated position by the force of the magnet 21 until it has been heated to its critical temperature. Upon being heated to this critical temperature, the work immediately loses all of its magnetic properties and conseently will rise to the surface of the lead bat The critical temperature is the temperature at which certain metallic parts should be quenched in order to effect the proper hardening thereof and hence when the work rises to the surface of the lead bath it will serve to positively indicate that the critical temperature has been reached. By this simple and unique apparatus an operator may easil and quckly ascertain when the work has een heated to the proper tem erature preliminary to the quenching thereo and as a result the process' of heat treating parts is greatly facilitated.

It is to be understood that the invention is not limited to the exact construction herein described and that the appended claims have been d-awn to define modifications which come within the true spirit and scope of the invention.

What is claimed is: v

1. In heat treating apparatus, a bath of treating material for the reception of work having a lower specific gravity than the treating material, means for heating the bath, and magnetic means :for retaining work within the lower portion of the bath until the work has been heated to a predetermined temperaof greater s ecific gravity than the articles to be treated or receiving a lurality of indiacriminately arran ed artic es, and an electromagnet positione adjacentthe bath for retaining the articles submerged therein `until 4 they are heated to the temperature at which they lose their. magnetism when the buoyant force of the bath is effective for changing the position of the articles.

In witness whereof, we hereunto subscribe our names this 29 da of October A. D., 1926.

- CLA NCE ROSS GALE STEWART.

CLARENCE JOHN ZERI.

ture when work is freed from the influence of\ the magnetic field and changes its position.

2. In heat treating apparatus, a bath of treating material having a relativel high specific gravity for the reception o work having a lower specific gravty, means for 'heating the bath, and an electro-magnet positioned externally of the bath for retainin -work within thebottom of the bath unt 4 and thereby indicates the completion of the heat treatment.

4. In a heat treating apparatus, a bath of treatin material for the reception of work, means or heating the bath, an electromagnet ositioned beneath the bath which is efl'ective or retaining the work submerged until it attains a predetermined temperature -when it is automatically released and rises to the surface %f %he bath due to the buoyant force of the at- 5. An apparatus for heat treating ferrou articles, comprising a bath oftreatin material of greater specific gravity than t e articles to be treated, means for heating the bath, and magnetic means for retaining the articles submerged in the bath until they reach a critical temperature when they are freed from the action of the magnetic means and change their position;

6. An apparatus for heat treating ferrous articles, comprising a bath of molten metal of greater specificgravity than the articles to be treated, and a'n electromagnet postioned adjacent the bath for retaining the articles submerged therein until they are heated to the temperature at which they lose their magnetism when due to the buoyant force of the bath they change their osition.

7. An apparatus for eat treating ferrous articles, comprising a bath of molten metal 

